Neuro phys

Question 1

The ridge of your fingerprint has what sensory receptors in it?

Answer 1

Merkel’s disk

Meissner’s corpuscles

Question 2

Where is the primary sensory neuron located?

Answer 2

Dorsal Root Ganglion

Question 3

What kind of receptor reacts to a stimulus by generating an AP initially, but does not last the entire time the stimulus is applied?

Answer 3

rapidly adapting receptor

Question 4

What is the mechanosensory pathway starting in the DRG and ascending?

Answer 4

• DRG
• into dorsal horn and ascend in dorsal funiculus
• synapse in cuneate nucleus where it decussates and goes through internal arcuate fibers
• to the medial lemniscus through the midbrain
• to the VPL nucleus of the thalamus
• then on to the somatosensory cortex

Question 5

What pathway do pain and temperature take in their ascension starting at the DRG?

Answer 5

• DRG
• into DH, decussate at that level through white commissure
• hop into lateral spinothalamic tract and ascend all the way to the VPL nucleus of the thalamus

Question 6

What are SA receptor subtype examples and what information do they collect?

Answer 6

Merkel’s disk - skin distortion/touch

Ruffini’s ending - skin distortion/pressure and stretch

Question 7

What are examples of RA receptor subtypes and what do they do?

How do they work?

Answer 7

Meissner’s corpuscles - texture, flutter from vibration

Pacinian corpuscle - (very RA) vibration - use of tools

both of these are fluid-filled - can see with structure

Question 8

On a rough surface, what sensory receptors are firing?

Answer 8

both Merkel and Pacinian receptors

Question 9

What receptor senses cool temperatures and menthol?

Answer 9

TRPM8

Question 10

What receptor senses noxious cold temp, mustard oil and propofol?

Answer 10

TRPA1

Question 11

What receptor senses noxious heat and capsaicin?

Answer 11

TRPV1

Question 12

What receptors sense heat or warmth?

Answer 12

TRPV1, V2, V3, V4

Question 13

For high resolution and better 2 point descrimination we want (smaller/larger) receptive field.

Answer 13

smaller

Question 14

What enhances acuity of sensory reception/perception? How does this work?

Answer 14

lateral inhibition - uses GABA to inhibit areas that are lateral to the stimulus

Question 15

The blood-nerve barrier is created by what two layers?

Answer 15

perineurium and endothelium

Question 16

What Sunderland score has a damaged axon, Schwann cell, and endoneurium? What is this called?

Answer 16

Sunderland 3 - Axonotmesis

Question 17

The surgeon should definitely do something if there is a Sunderland … because…

Answer 17

Sunderland 4 - severe axonotmesis

axon, schwann, endoneurium, and perineurium damage; intact epineurium allows very small amount of recovery

Question 18

Neurotmesis is considered…

Answer 18

Sunderland 5

nerve is completely severed; no recovery without surgery

Question 19

Neurpraxia is considered…

Answer 19

Sunderland 1

damage to Schwann cells and myelin

Question 20

Axon damage results in Wallerian degeneration. What is that?

Answer 20

distal to injury, a controlled inflammatory response, clears axonal and myelin debris

‘axons won’t sprout if myelin debris is about’

Question 21

Within 24-36 h after axonal fragmentation, healthy Schwann cells release what?

Answer 21

TNF alpha and IL-1B (pro-inflammatory cytokines) to activate macrophages

Question 22

What do TNF alpha and IL-1B produce in order to induce Schwann cell proliferation and phenotype switch?

Answer 22

GM-CSF

Question 23

What is a cytokine produced by Schwann cells and fibroblasts made to recruit circulating monocytes?

Answer 23

MCP-1

Question 24

During 48-72 hours s/p axon damage, more macrophages are present and MCP-1 is helping recruit. Schwann cells align longitudinally along the intact basal lamina and create…

Answer 24

Bands of Bungner

for a guide for axon regeneration

Question 25

Also during 48-72 hour s/p axon damage, macrophages will…

Answer 25

produce anti-inflammatory cytokines like IL-10 to combat TNFalpha and IL-1B

Question 26

3-7 days s/p axon damage, the Schwann cells in the Bands of Bungner configuration release what?

What do these things do?

Answer 26

growth factors - Nerve GF (NGF) and Brain Derived Neurotrophic Factor (BDNF)

induce axonal sprout and guide growing axon

Question 27

7-21 days after axon damage is about the end of the inflammatory response. How quickly are the axons able to grow back?

Answer 27

return of function if injury was a Sunderland 3 or less will occur with 1-4 mm/day

Question 28

If an axonal injury was classified as a Sunderland 4 or 5 and there is not efficient regrowth but some axons are still sprouting, what may result?

Answer 28

axons sprouting can form bundle of un-innervated nerve fibers - neuroma

severe pain, often requires surgery

Question 29

What is necessary to do for all surgical nerve repairs?

Answer 29

nerve debridement to prevent scar tissue formation

Question 30

What is the best option for nerve repair if the gap is <5 mm?

Answer 30

neurrhaphy - direct reattachment of ends

epineural neurrhaphy doesn’t gaurentee good fasicular alignment but is probably used most

Question 31

What is the best thing to do if the nerve gap is >5mm?

Answer 31

transplant nerves to bridge gap - autograph - sural nerve often used

Question 32

What is a benefit of neural grafts?

Answer 32

Wallerian degeneration and self -repair occurs

Question 33

What Na channels does a neuroma upregulate, possibly creating more pain? How can you decrease a pt’s neuroma pain?

Answer 33

Nav 1.8 and 1.9

Surgically remove neuroma, then bury proximal end of the nerve in muscle to prevent regeneration